OSRAM Develops Blue Thin-Film LEDs

SAN JOSE, Calif., Sept. 3 --OSRAM Opto Semiconductors announced today it has introduced blue thin-film light-emitting diodes (LEDs), which it calls an industry first.

OSRAM said the LEDs were developed with its indium gallium nitride-based, ThinGaN technology, which enables it to extract up to 75 percent of the internally generated light from the chip. A ThinGaN chip consists of an indium gallium nitride (InGaN)-on-sapphire chip, which is metallized and bonded to a carrier wafer.

The standard substrate material for blue LEDs is based on InGaN/silicon carbide (SiC), with a typical substrate thickness of 250 um. Chemically and mechanically, it is very stable and cannot be completely removed with either a wet chemical process or dry chemical plasma processes without also destroying the 5-um-thin InGaN epitaxial layer. Alternatively, sapphire is suitable as a standard substrate for InGaN epitaxy. However, the material properties of sapphire cause major distortions and defects during InGaN growth, which reduce the internal luminous efficacy, OSRAM said.

OSRAM said it has tailored the epitaxial procedure specifically to this material and at the same time developed a method for careful removal of the substrate material.

"In the world's first production-scale laser lift-off plant, the light from a pulsed ultraviolet laser splits up the semiconductor material into its components. It is then cleanly separated from the sapphire substrate," the company said in a statement.

OSRAM said it will begin series production of the LEDs in 2004.
For more information, visit: www.osram-os.com